Comparative study of E⋯N (E = Se/Te) intramolecular interactions in organochalcogen compounds using density functional theory

The intramolecular E⋯N (E = Se, Te) interactions between the selenium (and tellurium) and the nitrogen atom in four series of o-substituted organochalcogen compounds have been analyzed using density functional theory. The nature and the strength of this interactions and their dependence on substituents and the rigidity are predicted using B3LYP/6-31G(d)/LanL2DZ method. The strength of these E⋯N interactions are found to be dependent on the nature of EX (X = Cl, Br, I, SPh, CH2Ph; Ph: Phenyl) acceptor orbitals and follows the order I > Br > Cl > SPh > CH2Ph. The Natural Bond Orbital (NBO) analysis using DFT methods points to nN→σE−X* electron delocalization as the key contributing factor toward E⋯N nonbonding interactions. Both NBO and AIM methods suggest that the intramolecular interaction in these compounds is dominantly covalent in nature. Studies on the effect of solvent on the E⋯N interactions show that polar solvent stabilizes these interactions by shortening the E⋯N distances.